RamDisk and RamDisk Plus - Raxco Softwareftp.raxco.com/pub/download/rd/UserGuides/RamDisk_UserGuide.pdf · RamDisk and RamDisk Plus allow you to add, ... can be preserved across system

RamDisk and RamDisk Plus

What are RamDisk and RamDisk Plus?

RamDisk and RamDisk Plus allow you to add, modify and remove RAM disks from your system.RamDisk Plus allows you to add multiple RAM disks, supports variety of different kinds of RAMdisks, and can load a RAM disk image file, presenting its contents as a read-only disk. Inaddition, RamDisk Plus provides the ability to access main memory that many Windows®32-bit editions do not support.

SuperSpeed's RamDisk products are also used in embedded environments, and our RAM diskshave been deployed as bootable RAM disks.

Copyright © 2012 SuperSpeed LLC. All rights reserved.

SuperSpeed®, SuperCache®, SuperCache II®, SuperVolume®, and RamDisk Plus® areregistered trademarks of SuperSpeed LLC.

Microsoft, Windows, Windows 2000, Windows XP, Windows Vista, Windows 7, Windows Server2003, Windows Server 2003 R2, Windows Server 2008, and Windows Server 2008 R2 aretrademarks of Microsoft Corporation.

This software may be protected by one or more of the following patents: US patent numbers5,577,226, 5,606,681, 5,918,244, 6,370,615, 6,629,201, 6,651,136, 7,017,013, 7,039,767,7,111,129, 7,475,186, 7,594,068, 7,631,139, and other patents pending.

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http://www.superspeed.com

RamDisk Plus

RamDisk Plus features a host of options to maximize performance and utility. RamDisk Plussupports up to 99 RAM disks. Each RAM disk can be built on specific NUMA nodes. On PAEmachines, RAM disks can be created from memory not managed by Windows (ie. UnmanagedMemory), recapturing that lost system resource.

RamDisk Plus also features full management of a RAM disk's image file. A RAM disk's contentscan be preserved across system restarts making it behave very much like a hard drive. It'scontents can also be backed up and restored to user-specified files. In addition, image filescan be loaded as read-only disks and their contents browsed and extracted.

Depending on the system, RAM disks as large as 63 GB (32-bit) or 16 TB (64-bit) can becreated. The RAM disk can identify itself to Windows as a hard disk, as a removable-mediadisk, or as a virtual disk. It can be formatted with any Windows-supported file system.

Security features are also available with RamDisk Plus. The 'zero' option ensures that theentire contents of a RAM disk is zeroed (wiped clean) when it is removed from the system orwhen a new image is restored to it. The Auto-Wipe feature zeroes (wipes clean) the contentsof each RAM disk present in the system and reloads its initial (boot) image each time a userlogs out. This is useful in a secure environment where multiple users have access to aworkstation and its resources, but only one at a time, and the contents of RAM disk resourcesmust be completely destroyed at the end of a user session.

RAM disks are available to the system very early in system startup. Therefore, anyapplications or services that depend on the RAM disk can access it as soon as they start.

RAM disks created with RamDisk Plus also support page files.

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RamDisk

RamDisk allows you to create a single RAM disk using available physical memory from Windows.Depending on the system, a RAM disk as large as 63 GB (32-bit) or 16 TB (64-bit) can becreated. The RAM disk can appear to Windows as a hard disk, as a removable-media disk, oras a virtual disk. It can be formatted with any Windows-supported file system.

An important feature of RamDisk is that the RAM disk it creates is available to the system veryearly in system startup. Therefore, any applications or services that depend on the RAM diskcan access it as soon as they start.

RamDisk provides basic, simple support for a single RAM disk. For multi-disk, data persistence,NUMA, Unmanaged Memory support, auto-wipe (security), and other features, see RamDiskPlus.

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File menu commands

The File menu offers the following commands:

Auto-Wipe (dialog) Display status of and configure the auto-wipe-at-logoff service.

Licensing (dialog) Display and update licensing information.

Memory (dialog) Display and configure memory information.

Options (dialog) Display and set application options.

Exit Exits the application.

Action menu commands

The Action menu offers the following commands*:

Add (property sheet) Adds a new RAM disk to the system.

Add (simple wizard) Adds a new RAM disk to the system with basic options.

Add (advanced wizard) Adds a new RAM disk to the system with all options.

Load (property sheet) Loads a new RAM disk to the system from an image file.

Load (simple wizard) Loads a new RAM disk to the system from an image file with basic options.

Load (advanced wizard) Loads a new RAM disk to the system from an image file with all options.

View (property sheet) Views the contents of a RAM disk image file.

View (wizard) Views the contents of a RAM disk image file.

Save (dialog) Saves the contents of a RAM disk to its associated image file.

Backup (dialog) Backs up the contents of a RAM disk to an image file.

Restore (dialog) Restores the contents of a RAM disk from an image file.

Remove (dialog) Removes a RAM disk or an Image View from the system.

Properties (property sheet) Display and modify the properties of a RAM disk or an Image View.

Help menu commands

The Help menu offers the following commands, which provide you assistance with thisapplication:

Help Topics (new window) Offers you an index to topics on which you can get help.

About (dialog) Displays the version number of the application.

*The type of graphical user element (ie. property sheet, simple or advanced wizard) that theAdd, Load and View commands use is determined by the Options settings.

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Save dialog

Do not enforce volume locking

This option allows the RAM disk to be written to its associated image file without locking thestorage volume(s) present on the RAM disk. This means that handles may still be opened tothe disk when it is saved.

WARNING: Using this option can result in an image file that contains corrupt files and/or filesystems.

Because of the risks involved, this option generally is used only when it is impossible to closeall handles to the RAM disk.

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Backup RAM Disk dialog

Image file

Describes the path of the file to which the RAM disk's image will be saved.

Volume locking

This option allows the RAM disk to be written to its associated image file without locking thestorage volume(s) present on the RAM disk. This means that handles may still be opened tothe disk when it is saved.

WARNING: Using this option can result in an image file that contains corrupt files and/or filesystems.

Because of the risks involved, this option generally is used only when it is impossible to closeall handles to the RAM disk.

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Restore dialog

Image file

Describes the path of the file from which the RAM disk's image will be restored.

Zero memory before restoring

Select this option to completely erase (destroy) the contents of the RAM disk before restoringits contents with the selected image file.

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Remove dialog

Keep image file

Select this option to preserve the RAM disk's associated image file. The RAM disk can later bere-instantiated with the image file's contents using the 'Load RAM disk' command.

Zero memory

Select this option to completely erase (destroy) the contents of the RAM disk.

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Auto-Wipe dialog

Information

This dialog configures and displays the current status of the auto-wipe feature. This feature isavailable only for RamDisk Plus.

Install/Uninstall

Click to Install/Uninstall the auto-wipe-at-logoff service.

Important:

This feature is intended for use in secure environments where one and only one user is loggedon to the machine at any time. When this feature is enabled, the auto-wipe service willmonitor all user logon and logoff events. At logoff, the service will dismount each RAM diskpresent in the system, zero (wipe) its contents, and then restore its original image using itsassociated image file.

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About dialog

This dialog displays information about the product and application, including their version andcopyright.

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Licensing dialog

Information

This dialog displays information about the product's license, including the status, licensee,product(s) and platform(s) licensed, copyright, etc.

Update Key

Click this button to update the software license.

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Update Key dialog

Information

This dialog displays information about the product's license, including the status, licensee,product(s) and platform(s) licensed, copyright, etc.

License file

The location of the license key file.

Apply

Click to update (replace) the active key with the new key specified by the license file.

Browse...

Click to browse for the new license key file.

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Memory Information dialog

Page size

The size of a physical page of memory, in bytes.

NUMA node count

The number of NUMA (Non-Uniform Memory Architecture) nodes reported by the system.

NUMA node mask

The hexadecimal mask of the NUMA nodes reported by the system.

Memory available

Displays information about amounts of memory installed, available and reported by Windows. IfUnmanaged Memory (UM, memory not managed by Windows) is configured, information aboutit is also included.

PFN Info

Click this button for information about available PFN ranges.

Unmanaged

Click this button to view and configure Unmanaged Memory.

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PFN Information dialog

This dialog displays PFN information only if Unmanaged Memory has been configured for DirectAddress. Direct Address supports the creation of RAM disks in areas of contiguous physicalmemory, at specific physical memory addresses.

Page size

The size of a physical page of memory, in bytes.

First unmanaged PFN

The first PFN (Page Frame Number) after the last PFN reported as managed by the system.

Last detected PFN

The last PFN detected as valid memory.

Available PFN ranges

A list of ranges of unallocated PFNs.

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Unmanaged Memory Information dialog

Active values are those currently in use by the Virtual bus device. Pending values are thosethat will be in use when the Virtual bus device is restarted.

Installed (MB)

The amount of system RAM (main memory) installed, in megabytes.

Reserved (MB)

The amount of system RAM (main memory) reserved for use by a video adapter, the systemBIOS, etc.

Direct Address

Disabled for dynamic allocation of unmanaged memory. Enabled for direct address ofunmanaged memory.

Configure

Click this button to configure Unmanaged Memory.

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Configure Unmanaged Memory dialog

Enable use of Unmanaged Memory

Select to enable the use of Unmanaged Memory (UM).

Use System Management BIOS value

Select to use the amount of system RAM (main memory) reported by the System ManagementBIOS as the Installed value. At times the value reported using the System Management BIOSAPI may not be accurate. This option permits the Installed amount to be entered manually.

Automatically search for Reserved value

Select to search the physical memory address space for the Reserved value of system RAM(main memory). At times the value determined by the software may not be accurate. Thisoption permits the Reserved amount to be entered manually.

Installed (MB)

The amount of system RAM (main memory) installed, in megabytes.

Reserved (MB)

The amount of system RAM (main memory) reserved for use by a video adapter, the systemBIOS, etc. If the system shares main memory with a video adapter, the amount of reservedmemory may depend on the resolution and color depth of the display.

Direct Address

Disable for dynamic allocation of unmanaged memory. Dynamic allocation allows unmanagedmemory to be allocated dynamically along with the memory managed by Windows.

Enable for direct address of unmanaged memory. Direct address allows a RAM disk to beallocated from unmanaged memory as a single block of contiguous pages.

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Options dialog

User interface method

The operations to add or load a RAM disk or to view a RAM disk image file have many optionswhich can be confusing. The wizards present the various options in a logical sequence. Forstep-by-step access to the options, select Use wizards. To see only the most frequentlyused options, unselect Use advanced wizards. To see all the available options, select Useadvanced wizards. For quick access to all options, select Use property sheets.

Main window

Remember window placement

Saves the desktop location of the application's window when it is closed.

Remember window size

Saves the size of the application's window when it is closed.

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NUMA Nodes dialog

Memory allocation nodes

Selects the NUMA nodes from which memory will be allocated. NOTE: If unmanaged memory isconfigured, memory for the RAM disk will be allocated from unmanaged memory first. NUMAaffinity information is not available for unmanaged memory, so the nodes here selected will beignored.

Select all

Check this box to allocate RAM disk memory from all NUMA nodes.

Clear all

Click this button to unselect all NUMA nodes. At least one node must be selected to create aRAM disk.

0, 1, 2, 3, ...

The individual NUMA nodes from which the RAM disk allocation will be made. On NUMAmachines, a RAM disk's allocation is composed of a series of 1 MB allocations, each taken froma NUMA node in the selection, in round-robin fashion

.

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Progress dialog

This dialog displays progress activity for a particular operation.

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Add - Advanced Wizard

This wizard presents all the available options for creating a new RAM disk. Its advantage overthe Add property sheet is the logical order in which the options are presented. This helpsreduce confusion due to the interdependency of many of the options.

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Size advanced wizard page

Size of the RAM disk, in megabytes

Specify the size of the RAM disk to be created. The maximum size is limited by the amount ofphysical memory (RAM) installed in the system.

Zero memory when removed or restored

Select to zero (erase) the contents of the entire RAM disk when it is removed or when animage is restored to it.

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Allocation Source advanced wizard page

Allocate from Windows-managed memory

Select to allocate the RAM disk's memory from memory managed by Windows. NOTE: IfUnmanaged Memory (UM) is configured, allocations will first be attempted from UM and thenfrom Windows.

Direct address memory NOT managed by Windows

Select to allocate the RAM disk's memory from memory not managed by Windows, or Unmanaged Memory (UM). This option is only available if UM is configured with Direct Addressenabled.

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NUMA Nodes advanced wizard page

Selects the NUMA nodes from which memory will be allocated. NOTE: If Unmanaged Memory(UM) is configured, memory for the RAM disk will be allocated from UM first. NUMA affinityinformation is not available for UM, so the selected nodes will be ignored for UM allocations.

Select all


Clear all


0, 1, 2, 3, ...

The individual NUMA nodes from which the RAM disk allocation will be made. On NUMAmachines, a RAM disk's allocation is composed of a series of 1 MB allocations, each taken froma NUMA node in the selection, in round-robin fashion.

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Base PFN advanced wizard page

Automatically assign PFN

Select to allow the application to choose the PFN.

Manually assign PFN base / Base PFN

Select to enter the base PFN of the physical memory range which the RAM disk will occupy, inhexadecimal.

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Device Type advanced wizard page

Partitionable - detected by Windows as a hard disk

Select to create a RAM disk that Windows will detect as a hard disk. This disk will support apartition table, and can be managed by the Disk Management MMC.

Removable - detected by Windows as a removable media device

Select to create a RAM disk that Windows will detect as a hard disk with removable media.

Virtual - detected by Windows as a RAM disk

Select to create a RAM disk that Windows will detect as RAM disk, not a hard disk. This diskwill not support a partition table.

Version 8.0 - compatible with previous versions of RamDisk

Select to create a RAM disk that is compatible with RamDisk 8.0 and RamDisk Plus 8.0.

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Partitioning advanced wizard page

Create a partition table

Select to create a partition table. NOTE: This option is not available for version 8 RAM disks,nor for virtual RAM disks.

Use a GUID partition table

Select to create a GUID-type partition table. NOTE: This option is valid on 64-bit platformsonly.

Create a partition table entry

Select to insert an entry in the partition table. The partition entry will span the entire RAMdisk.

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Drive Letter and File System advanced wizard page

Specify the drive letter to assign the RAM disk

Select a drive letter to assign to the partition of a RAM disk containing a partition table andentry, or, in the case of a version 8 RAM disk or a virtual disk (which have no partition table),to the disk itself.

Specify the file system to format the RAM disk

Select a file system format for the partition of a RAM disk containing a partition table andentry, or, in the case of a version 8 RAM disk (which has no partition table), for the disk itself.Note: if selected, a virtual disk is formatted by the class driver at the time of its creation witha FAT-type file system only.

Create '\temp' folder

Select to create a folder named "temp" in the root of the RAM disk.

Compress file system

Select to compress the contents of the entire file system. For NTFS only.

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Associated Image File advanced wizard page

Use associated image file

Select to create and maintain an image file that is associated with the RAM disk. For RAMdisks containing a partition table and for version 8 RAM disks the associated image file is usedto save or restore disk's contents between system reboots. This feature is especiallyimportant since for such RAM disks any file system metadata (eg. the "format" information) islost when the system is shutdown or restarted. When a RAM disk with an associated image fileis re-instantiated, its image is read from the image file, thus restoring the file system and anyother saved data. Without the associated image file, such a RAM disk will have no file systemat all when the system is started. NOTE: generally, virtual RAM disks are formatted at thetime they are instantiated and so do not require an associated image file.

Location of associated image file

Specifies the drive letter of the root directory in which the RAM disk's associated image filewill be placed. A RAM disk's associated image file is always located in the root directory of adrive. By default, it is located in the root of the boot drive (the partition containing the activeWindows installation). The file is marked hidden. Its name is "SsRdXxxx.cif", where Xxxxrepresents the four-digit identifier assigned to the RAM disk.

Save at system shutdown

Select to save the contents of the RAM disk to its associated image file at system shutdown.This option effectively makes the RAM disk persistent across reboots.

Reserve space for full disk

Select to expand the size of the associated image file to the largest necessary to contain theentire RAM disk's contents. This option does not specify that the entire RAM disk be saved. Itspecified that sufficient space be reserved on the partition containing the associated imagefile, so that if the entire RAM disk had to be saved it could be.

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Add - Simple Wizard

This wizard presents the most frequently used options for creating a new RAM disk.

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Size wizard page

Specify the size of the RAM disk, in megabytes


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Drive Letter wizard page


Select a drive letter to assign the RAM disk. Drive letters already used by local drives are notshown. Take care not to select a drive letter that is used by a network drive.

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File System wizard page







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Save at Shutdown wizard page



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Zero Contents wizard page



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Load - Advanced Wizard

This wizard presents all the available options for creating a RAM disk from an existing imagefile. Its advantage over the property sheet is the logical order in which the options arepresented. This helps reduce confusion due to the interdependency of many of the options.

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Image File advanced wizard page

Select the root directory containing the associated image file

Specify the drive letter of the root directory in which the RAM disk's associated image file islocated. A RAM disk's associated image file is always located in the root directory of a drive.By default, the file is placed in the root of the boot drive (the partition containing the activeWindows installation).

Select the associated image file's identifier

Specify the four-digit identifier of the RAM disk's image file. When a RAM disk is initiallycreated, it is assigned a four-digit identifier. This identifier uniquely identifies the disk. If thedisk is created with an associated image file, the file's name and contents are linked to theRAM disk using the identifier. As long as the RAM disk remains in the system, its identifier willnot change.

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Allocation Source advanced wizard page





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NUMA Nodes advanced wizard page

Selects the NUMA nodes from which memory will be allocated. NOTE: If Unmanaged Memory(UM) is configured, memory for the RAM disk will be allocated from UM first. NUMA affinityinformation is not available for UM, so the selected nodes will be ignored for UM allocations.

Select all


Clear all


0, 1, 2, 3, ...

The individual NUMA nodes from which the RAM disk allocation will be made. On NUMAmachines, a RAM disk's allocation is composed of a series of 1 MB allocations, each taken froma NUMA node in the selection, in round-robin fashion.

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Base PFN advanced wizard page



Manually assign PFN base / Base PFN

Select to enter the base PFN of the physical memory range which the RAM disk will occupy, inhexadecimal.

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Drive Letter advanced wizard page



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Save at Shutdown advanced wizard page

Automatically save the RAM disk's contents at system shutdown


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Load - Simple Wizard

This wizard presents the most frequently used options for creating a RAM disk from an existingimage file.

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Image File wizard page

Select the root directory containing the associated image file


Select the associated image file's identifier

Specify the four-digit identifier of the RAM disk's image file. When a RAM disk is initiallycreated, it is assigned a four-digit identifier. This identifier uniquely identifies the disk. If thedisk is created with an associated image file, the file's name and contents are linked to theRAM disk using the identifier. As long as the RAM disk remains in the system, its identifier willnot change.

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Select a drive letter to assign the RAM disk. Drive letters already used by local drives are notshown. Take care not to select a drive letter that is used by a network drive.

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Save at Shutdown wizard page



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View - Wizard

This wizard presents all the available options for creating a view of a RAM disk image that isstored in an image file. The view is effectively a read-only RAM disk. Only a minimal amount ofmemory is allocated to create the view.

Use image views to retrieve data from RAM disk image files stored on disk, without having tocreate a RAM disk. A view allows you to access a saved RAM image that may be much largerthan the amount of available memory.

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Image File wizard page

Image file location

Specify the path of the image file to be viewed.

Browse...

Click to open an "Open File" dialog box to browse for an image file.

Examine

Click to examine the contents of the specified file.

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Specify the drive letter to assign the read-only RAM disk

Select a drive letter to assign the read-only RAM disk. Drive letters already used by localdrives are not shown. Take care not to select a drive letter that is used by a network drive.

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Add - Property Sheet

This property sheet presents all the available options for creating a new RAM disk. Itsadvantage over the Add wizards is its immediate access to all the options.

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Size property page

Size of the RAM disk, in megabytes




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Memory property page



NUMA Nodes

Click to select from which NUMA nodes to allocate the RAM disk's memory. NOTE: This doesnot apply to UM allocations.





Base PFN

Enter the base PFN of the physical memory range which the RAM disk will occupy, inhexadecimal.

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Type property page

Partitionable - Windows hard disk

Select to create a RAM disk that Windows will detect as a hard disk. This disk will support apartition table, and can be managed by the Disk Management MMC.

Removable - Windows removable media device

Select to create a RAM disk that Windows will detect as a hard disk with removable media.

Virtual - Windows RAM disk

Select to create a RAM disk that Windows will detect as RAM disk, not a hard disk. This diskwill not support a partition table.

Version 8.0 - compatible with RamDisk 8.0

Select to create a RAM disk that is compatible with RamDisk 8.0 and RamDisk Plus 8.0.

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Partitioning property page

Create a partition table

Select to create a partition table. NOTE: This option is not available for version 8 RAM disks,nor for virtual RAM disks.

Use a GUID partition table

Select to create a GUID-type partition table. NOTE: This option is valid on 64-bit platformsonly.

Create a partition table entry

Select to insert an entry in the partition table. The partition entry will span the entire RAMdisk.

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Drive Letter and File System property page









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Image File property page




Specifies the drive letter of the root directory in which the RAM disk's associated image filewill be placed. A RAM disk's associated image file is always located in the root directory of adrive. By default, it is located in the root of the boot drive (the partition containing the activeWindows installation). The file is marked hidden. Its name is "SsRdXxxx.cif", where Xxxxrepresents the four-digit identifier assigned to the RAM disk.





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Load - Property Sheet

This property sheet presents all the available options for creating a RAM disk from an existingimage file. Its advantage over the Add wizards is its immediate access to all the options.

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Root directory of the Associated Image File


Associated Image File identifier

Specify the four-digit identifier of the RAM disk. When a RAM disk is initially created, it isassigned a four-digit identifier. This identifier uniquely identifies the disk. If the disk is createdwith an Associated Image File, the file's name and contents are linked to the RAM disk usingthe identifier. As long as the RAM disk remains in the system, its identifier will not change.

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Memory property page



NUMA Nodes

Click to select from which NUMA nodes to allocate the RAM disk's memory. NOTE: This doesnot apply to UM allocations.





Base PFN

Enter the base PFN of the physical memory range which the RAM disk will occupy, inhexadecimal.



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Drive Letter property page

Drive letter to assign the RAM disk


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Save at Shutdown property page

Automatically save the RAM disk's contents at system shutdown


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View - Property Sheet

This property sheet presents all the available options for creating a view of a RAM disk imagethat is stored in an image file. The view is effectively a read-only RAM disk. Only a minimalamount of memory is allocated to create the view.

Use image views to retrieve data from RAM disk image files stored on disk, without having tocreate a RAM disk. A view allows you to access a saved RAM image that may be much largerthan the amount of available memory.

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Image file location

Specify the path of the image file to be viewed.

Browse...

Click to open an "Open File" dialog box to browse for an image file.

Examine

Click to examine the contents of the specified file.

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Drive Letter property page

Drive letter to assign the read-only RAM disk

Select a drive letter to assign to the partition of a RAM disk image containing a partition tableand entry, or, in the case of a version 8 RAM disk or a virtual disk image (which have nopartition table), to the disk itself.

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Properties

This property sheet display the current RAM disk or Image View settings. It can also be usedto modify the settings.

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Properties page

Description

Details the properties of the RAM disk.

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Settings page

This page contains the changeable settings of the RAM disk.

Drive letter assigned to the RAM disk







Specifies the drive letter of the root directory in which the RAM disk's associated image filewill be located. A RAM disk's associated image file is always located in the root directory of adrive. By default, it is located in the root of the boot drive (the partition containing the activeWindows installation).





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The 32-bit Address Space

The following information pertains to processors capable of running 32-bit Microsoft Windowsoperating systems.

What is a 32-bit address space?

An address space is a logical area or space containing one or more locations that can beindividually accessed or addressed. A 32-bit address space describes an area containing amaximum possible 4,294,967,296 locations or addresses. A 32-bit operating system, therefore,would typically be limited to access 4,294,967,296 pieces of computer information, or bytes (4GB).

Address spaces on 32-bit Windows-compatible hardware

Computers that run Windows operating systems actually utilize two different kinds addressspaces: a memory address space and an I/O port address space. The memory address spaceis where main memory (RAM) is accessed, while devices (network, video, disk, etc.) typicallyuse both memory and I/O address spaces.

Furthermore, memory is accessed through two different kinds of address spaces: physical andvirtual. The virtual address space is what applications and processes "see" and use. One ofthe most important purposes of virtual address space is that it can present to applicationsand processes more memory than is physically present in the machine. A virtual address mayor may not correspond to a real, physical address. The physical address space is where real,physical memory, or memory-addressed devices, are accessed.

As noted above, a 32-bit processor's memory address space is used to access both mainmemory (RAM) and devices that require memory addresses. Since the devices (called"memory-mapped" devices) may consume a considerable amount of memory address space,much less than the full 4 GB address space may be available for accessing main memory. See Memory Managed by Windows to see how Windows handles this problem.

However, with special hardware and software, 32-bit processors can address much more than4 GB. See Physical Address Extensions for how this is possible.

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Physical Address Extensions (PAE)

What are Physical Address Extensions?

Physical Address Extensions, or PAE, are a set of hardware specifications that extend a 32-bitprocessor's physical memory address space to a maximum of 36 bits, thus providing supportfor up to 64 gigabytes of memory. Depending on the hardware, the memory address spacemay be 33, 34, 35 or 36 bits wide. These represent 8, 16, 32, and 64 gigabyte addressspaces.

It's worth repeating that PAE defines hardware that supports physical address spaces largerthan 32 bits. However, taking advantage of these larger address spaces requires more than aPAE-compatible processor and chipset (on the mainboard): it requires a PAE-enabled operatingsystem. Operating systems that are "unaware" of PAE will run on PAE hardware but "see" onlya 32-bit (4 GB) address space.

Happily, all 32-bit Windows operating systems from Windows 2000 forward support PAE mode.See Memory Managed by Windows for more about how Windows supports PAE. SeeUnmanaged Memory for information about how RamDisk Plus supports PAE.

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Memory Managed by Windows

Non-PAE Systems

Windows operating systems come in two basic editions: 32-bit and 64-bit. Logically, 32-biteditions of Windows run on 32-bit processors, many of which, along with their chipset,implement 32-bit memory and I/O address buses. These non-PAE machines can address amaximum of 4,294,967,296 bytes (4 gigabytes, GB), per address space. (For more about PAE,see Physical Address Extensions.)

On Windows computers, the base 4 GB memory address space is not devoted exclusively tomain memory. Video, network, disk, and other devices also require memory address space.Because of this, only a reduced amount of the 4 GB address space is actually available tomain memory.

In order to eliminate a host of problems associated with the device drivers that requirememory address space, starting with Windows XP SP2 Microsoft has limited the amount ofmain memory accessible in the 4 GB address space to approximately 3.2 GB. Therefore, even ifa non-PAE machine has more than 3.2 GB of main memory installed, only 3.2 GB of it will beaccessible to Windows. The remaining 0.8 GB of address space is reserved formemory-mapped devices.

For machines that do not have PAE hardware, this access limit to main memory cannot beovercome. It is a hardware limitation.

PAE Systems

On machines with PAE hardware, all main memory can be access -- at least theoretically. ForWindows to access the memory, it must also be running in PAE mode. All 32-bit Windowsoperating systems from Windows NT 4.0 forward support PAE, including 32-bit Windows XP,Vista and 7. To determine if Windows is running in PAE mode, open the System Propertiesdialog and select the General tab. If PAE is enabled the text "Physical Address Extensions" willappear near the bottom of the dialog.

Depending on the edition and applied service pack, Windows operating systems providedifferent facilities for enabling PAE. (See “Boot Parameters to Configure DEP and PAE” http://msdn.microsoft.com/en-us/library/aa468629.aspx, “/noexecute”http://msdn.microsoft.com/en-us/library/ms791539.aspx, “/execute”http://msdn.microsoft.com/en-us/library/aa468631.aspx, “/nopae”http://msdn.microsoft.com/en-us/library/ms791508.aspx, “/pae”http://msdn.microsoft.com/en-us/library/ms791485.aspx.)

On PAE-enabled machines, Windows versions from XP SP2 forward still dedicate the upper 0.8GB of the first 4 GB of memory address space to memory-mapped devices. However, ifWindows is running with PAE mode enabled, then it is capable of accessing whatever amountmain memory is installed after the first 3.2 GB, up to a total of 64 GB. This memory simply willbe mapped to start above the first 4 GB of address space. In other words, assuming themachine has more than 3.2 GB of main memory, the first 3.2 GB of memory will be accessible inthe lower 3.2 GB of memory address space, while the remaining main memory will be accessibleat addresses starting at and above 4.0 GB.

Even so, Microsoft has imposed limits on what each edition of 32-bit Windows will access, ormanage, even if PAE mode is enabled. Here are the limits:

32-bit Windows Edition Maximum managed memory (GB)

w/o PAE w/PAE

Windows XP SP2, Windows Vista, Windows7 3.2 3.2

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Windows Server 2003, 2003 R2, 2008,2008 R2, Standard edition or lesser 3.2 4.0

Notice that Windows XP SP2, Windows Vista and Windows 7 have the same memory limitswhether running in PAE mode or not.

Overcoming the Windows Memory Barrier

The fact is, with "extra help" all 32-bit PAE-enabled editions of Windows can support up to 64GB of main memory -- the PAE hardware limit. SuperSpeed's RamDisk Plus product providesthat "extra help" by supporting what we call "Unmanaged Memory". See Unmanaged Memoryfor information about how RamDisk Plus supports memory not managed by Windows.

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Unmanaged Memory

With PAE-mode enabled, all 32-bit Windows editions can potentially access up to 64 GB ofmain memory. Nonetheless, different Windows editions limit the amount of main memory theysupport to 4 GB or less.

SuperSpeed's RamDisk Plus features support to utilize main memory that Windows does not.

What is unmanaged memory?

We call the main memory that Windows does not use or manage "Unmanaged Memory", or UM.On a machine running 32-bit Windows XP SP2, Windows Vista, or Windows 7 with 4 GB of mainmemory installed and with PAE mode enabled, Windows typically limits the amount of mainmemory available to about 3.2 GB. This leaves about 0.8 GB of main memory unused orunmanaged by Windows.

With RamDisk Plus, that 0.8 GB of main memory unused or unmanaged by Windows(Unmanaged Memory, UM) can now be put to work! What's more, UM can be used right alongwith the physical memory that Windows manages. In the case described above, RamDisk Pluscan create a RAM disk as large as 3.5 GB! On a machine running 32-bit Windows XP SP2 orVista with 8 GB of main memory installed and with PAE mode enabled, a RAM disk up to 7.5 GBcan be created!

Put as Much RAM as You Have and Need to Work

RamDisk Plus thus reclaims the memory resources that would otherwise be lost or unusable.This provides greater versatility in the use of Windows operating systems and applicationsthat can benefit from the increased performance afforded by RAM disks. Now any 32-bitPAE-enabled edition of Windows can access up to 64 GB of main memory, using the bulk of itto enhance system performance!

RamDisk Plus supports two methods to access UM: dynamic and static. Dynamic access, or dynamic allocation, allows UM to be used transparently along with the physical memorymanaged by Windows. Static access, or direct address, allows specific blocks of physicalmemory to be allocated for RAM disks.

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Dynamic Allocation of Unmanaged Memory

What is dynamic allocation?

Dynamic allocation allows Unmanaged Memory (UM) to be allocated in a fashion similar to howWindows allocates physical memory pages. When a RAM disk is created, memory is firstallocated from any unallocated UM, and then from unallocated Windows-managed memory.When a RAM disk is removed, the physical memory allocated to it is returned -- either to thepool of physical pages that Windows manages, or to the UM pool that RamDisk Plus manages.

For example, on a 32-bit, PAE-enabled Windows XP, Windows Vista or Windows 7 system with8 GB of main memory, typically about 3.2 GB is managed by the operating system. Ordinarily, aRAM disk of only some 2.5 GB could be created. With RamDisk Plus and the UM featureproperly configured, the additional 4.8 GB of UM also would be available. Therefore, a singleRAM disk of 7 GB or more (4.8 GB UM, 2+ GB Windows-managed) could be created.

Generally, dynamic allocation is as it offers the simplest and most flexible method to use UM.

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Direct Address of Unmanaged Memory

What is direct address?

Direct address allows Unmanaged Memory (UM) to be allocated as a single block of contiguousphysical memory pages. A base or starting physical address must be specified in the form of aPage Frame Number (PFN). The number of physical memory pages used for the RAM disk isdetermined by the RAM disk's size.

Generally, RAM disks created with direct address of UM are used in embedded environments.Direct address does NOT support RAM disks created from memory managed by Windows.

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Documents

RamDisk and RamDisk Plus - Raxco Softwareftp.raxco.com/pub/download/rd/UserGuides/RamDisk_UserGuide.pdf · RamDisk and RamDisk Plus allow you to add, ... can be preserved across system